Useful articles from various thermoplastic resins have been prepared from molds for many years. Injection molding provides a convenient way for preparing various articles from thermoplastic resins, particularly objects of a relatively intricate nature. In order to accomplish a release of the resin from the mold, various mold release agents have been found which provide for a release of the resin with lower ejection pressure. Such an agent should be chemically compatible with the resin as measured by the usual characteristics of the resin under normal conditions and heat treatments.
Of the thermoplastic resins which find a mold release agent useful from time to time one of the most sensitive to chemical interaction is the polycarbonates.
A series of patents disclosing the use of various carboxylic acid esters as mold release agents for polycarbonates have been recently issued: U.S. Pat. Nos. 4,065,436; 3,836,499; 4,131,575 and 3,784,595. Additionally carboxylic acid esters have been known as plasticizers for polycarbonate in U.S. Pat. No. 3,186,961. Still further Japanese patent publication No. 47-41092 discloses various esters including butyl stearate and the natural product beeswax as mold release agents for polycarbonate.
A new class of mold release agents for thermoplastic resins in general and polycarbonates in particular has been discovered.